Image forming apparatus and method

Abstract

An image forming apparatus utilizing two types of toners. The first toner is of a type that causes the charge thereon to increase over time, while the second toner is a type in which the charge decreases over time. The storage chamber for the apparatus holds a two-component developing agent formed of a carrier and a first toner. In proportion to the consumption of the first toner during the printing process, the second toner is resupplied from a toner hopper to the developing agent in the storage chamber.

What is claimed is: 
     
       1. An image forming apparatus comprising: storage means for initially storing a two-component developing agent containing a carrier and a first toner;   replenishment means for continuously resupplying a second toner to the two-component developing agent in the storage means in proportion to the consumption of the first toner, said first and second toners being of different types, the amount of charge on the first toner increasing with time and the amount of charge on the second toner decreasing with time; and   developing means for developing an electrostatic latent image by means of the two-component developing agent.   
     
     
       2. The image forming apparatus according to claim 1, wherein said first and second toners have different charging characteristics. 
     
     
       3. The image forming apparatus according to claim 1, wherein said first and second toners are formed of materials of different rank of frictional series. 
     
     
       4. The image forming apparatus according to claim 1, wherein the mixture of said first and second toners is allowed to have a substantially uniform charging characteristic even after the lapse of time by resupplying the second toner in proportion to the consumption of the first toner. 
     
     
       5. The image forming apparatus according to claim 1, wherein said second toner is formed of the mixture of the first toner and an additive. 
     
     
       6. The image forming apparatus according to claim 5, wherein said additive is formed of a one-component magnetic toner. 
     
     
       7. The image forming apparatus according to claim 6, wherein the mean particle diameter of said second toner ranges from 5 to 20 μm. 
     
     
       8. The image forming apparatus according to claim 5, wherein the additive content of said second toner is 1% or less by weight. 
     
     
       9. The image forming apparatus according to claim 1, wherein the mean particle diameter of said first toner ranges from 5 to 20 μm. 
     
     
       10. The image forming apparatus according to claim 1, wherein said storage means includes means for stirring the first and second toners. 
     
     
       11. An image forming apparatus comprising: storage means for storing a two-component developing agent formed of a toner and a carrier;   developing means for developing an electrostatic latent image by means of the two-component developing agent stored in the storage means;   replenishment means for continually resupplying the toner to the two-component developing agent in proportion to the amount of toner in the developing agent consumed by the developing means;   a first toner used as part of the toner of the two-component developing agent and is initially stored in the storage means; and   a second toner used as part of the toner of the two component developing agent and is supplied to the storage means by the replenishment means, said first and second toners being of different types, the amount of charge on the first toner increasing with time and the amount of charge on the second toner decreasing with time.   
     
     
       12. An image forming method for developing an electrostatic latent image by means of a two-component developing agent containing a first toner and a carrier; including the step of:   developing the electrostatic latent image by means of a two-component developing agent containing a first toner, a second toner, and a carrier, said first and second toners being of different types, said second toner being continuously resupplied to the two-component developing agent in proportion to the consumption of the first toner, the first and second toner contents of the developing agent decreasing and increasing, respectively, with developing time, while the amount of charge on the first toner increases with time and the amount of charge on the second toner decreases with time.